[Radiance-general] Display of time lapse at constant brightness

[Ruggiero Guida]

Just an additional note. objline does not produce the oblique view. I have
tested with the table.rad in the tutorial as well and the results is the
same.

Thanks


On 4 October 2015 at 01:18, Rob Guglielmetti <rob.guglielmetti at gmail.com>
wrote:

> Somehow my reply didn't go thru the first time, but the last 'graph speaks
> to this issue of tonemapped versus absolute value images...
>
> Another option for you Wouter would be to use the phisto shell script
> (assuming you're running Radiance on Mac or Linux). From the man page:
>
> "The primary function of this script is to precompute histograms for the
>        pcond(1) program, which may then be used to compute multiple,
> identical
>        exposures.   This is especially useful for animations and image
> compar-
>        isons."
>
> This is pretty much right up your alley, for animations. As this method
> uses tonemapping, you must remain mindful of what it is that you are really
> displaying. Perhaps the best method is to show, side-by-side, a
> tonemapped image alongside a quantitative falcesolor image of the real
> values.
>
> On Sat, Oct 3, 2015 at 11:12 AM, Chris Kallie <kallie at umn.edu> wrote:
>
>> In Wouter's post, he stated "In absolute terms one wall has a luminance
>> of 15 cd/m2 at 9:00. That
>> same wall is 29 cd/m2 at 12:00, yet when displayed (using ximage) it
>> appears darker."
>>
>> I would be interested to understand how the output images would remain
>> linear using a tone-mapping algorithm.
>>
>> The general issue at hand is that some people want visually pleasant
>> results, and some need numeric accuracy in the outputs. Perhaps the best
>> approach depends upon what the intended use of the output images is, imho.
>> (Unless I am not understanding something about the tone-mapping algorithm.)
>> -Chris
>>
>>
>> On 10/3/15 1:03 PM, Greg Ward wrote:
>>
>> Andy's recommendation would also be mine, but you need the "-I" option to
>> pcond to get it to read the histogram from stdin.
>>
>> Cheers,
>> -Greg
>>
>> *From: *Andy McNeil < <mcneil.andrew at gmail.com>mcneil.andrew at gmail.com>
>>
>> *Subject: *Re: [Radiance-general] Display of time lapse at constant
>> brightness
>>
>> *Date: *October 3, 2015 8:08:16 AM PDT
>>
>>
>> You could also use phisto to create a luminance histogram from all your
>> images and tone map your images using pcond with the all image histogram as
>> input.
>>
>> phisto frame*.hdr > allframes.hist
>> pcond frame0001.hdr < allframes.hist | ra_tiff - frame0001.tif
>>
>> When there's a wide range of illumination conditions I find that pcond
>> with the histogram works best to preserve visibility and maintain
>> consistency between frames.
>>
>> Andy
>>
>> On Sat, Oct 3, 2015 at 5:45 AM, Chris Kallie <kallie at umn.edu> wrote:
>>
>>> You can use the -e option in pfilt to adjust by a constant. Instead of
>>> using +0, you can use a value without the + symbol that is a fraction of
>>> the EXPOSURE value in your header file. -Chris
>>>
>>>
>>> On 10/3/15 8:21 AM, ascendilex | Wouter Beck wrote:
>>>
>>>> Dear Group,
>>>>
>>>> I'm trying to display a series of Radiance renderings as a time lapse
>>>> animation.
>>>>
>>>> I convert (pfilt -e +0 -r .6 -x /2 -y /2 filtered) hdr-images via
>>>> ra_tiff and the resulting tifs are combined into an animated gif via
>>>> (ImageMagick's) convert -delay 200 -quality 100 *.tif time-lapse.gif.
>>>>
>>>> Each image represents a view of an atrium 1 hour apart.
>>>> The indirectly lit walls of the room that contains my view point get
>>>> displayed darker as the atrium scene brightens up.
>>>> In absolute terms one wall has a luminance of 15 cd/m2 at 9:00. That
>>>> same wall is 29 cd/m2 at 12:00, yet when displayed (using ximage) it
>>>> appears darker.
>>>> Exposure times in the headers are of course quite different:
>>>> vp-A-092108.00.pic:EXPOSURE=3.008155e+00
>>>> vp-A-092112.00.pic:EXPOSURE=3.957302e-01
>>>>
>>>>
>>>> Basically I want the tone mapping according to a constant (perhaps log)
>>>> scale for all images.
>>>>
>>>> How can that be accomplished?
>>>> (Looks like falsecolor could do this if it also had a greyscale
>>>> palette.)
>>>>
>>>> Best regards,
>>>>
>>>> Wouter
>>>>
>>>>
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>>>
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